RNA-seq analyses reveal that cervical spinal cords and anterior motor neurons from amyotrophic lateral sclerosis subjects show reduced expression of mitochondrial DNA-encoded respiratory genes, and rhTFAM may correct this respiratory deficiency.

Amyotrophic lateral sclerosis (ALS) is a generally fatal neurodegenerative disease of adults that produces weakness and atrophy due to dysfunction and death of upper and lower motor neurons. We used RNA-sequencing (RNA-seq) to analyze expression of all mitochondrial DNA (mtDNA)-encoded respiratory genes in ALS and CTL human cervical spinal cords (hCSC) and isolated motor neurons. We analyzed with RNA-seq mtDNA gene expression in human neural stem cells (hNSC) exposed to recombinant human mitochondrial transcription factor A (rhTFAM), visualized in 3-dimensions clustered gene networks activated by rhTFAM, quantitated their interactions with other genes and determined their gene ontology (GO) families.

Mitochondria in the pathophysiology of Alzheimer's and Parkinson's diseases.

Mitochondria are responsible for the majority of energy production in energy-intensive tissues like brain, modulate Ca signaling and control initiation of cell death. Because of their extensive use of oxygen and lack of protective histone proteins, mitochondria are vulnerable to oxidative stress (ROS)-induced damage to their genome (mtDNA), respiratory chain proteins and ROS repair enzymes. Animal and cell models of PD use toxins that impair mitochondrial complex I activity.

The Alzheimer's disease mitochondrial cascade hypothesis: progress and perspectives.

Ten years ago we first proposed the Alzheimer's disease (AD) mitochondrial cascade hypothesis. This hypothesis maintains that gene inheritance defines an individual's baseline mitochondrial function; inherited and environmental factors determine rates at which mitochondrial function changes over time; and baseline mitochondrial function and mitochondrial change rates influence AD chronology. Our hypothesis unequivocally states in sporadic, late-onset AD, mitochondrial function affects amyloid precursor protein (APP) expression, APP processing, or beta amyloid (Aβ) accumulation and argues if an amyloid cascade truly exists, mitochondrial function triggers it.

RhTFAM treatment stimulates mitochondrial oxidative metabolism and improves memory in aged mice.

Mitochondrial function declines with age in postmitotic tissues such as brain, heart and skeletal muscle. Despite weekly exercise, aged mice showed substantial losses of mtDNA gene copy numbers and reductions in mtDNA gene transcription and mitobiogenesis signaling in brain and heart. We treated these mice with weekly intravenous injections of recombinant human mitochondrial transcription factor A (rhTFAM).

Recombinant human mitochondrial transcription factor A stimulates mitochondrial biogenesis and ATP synthesis, improves motor function after MPTP, reduces oxidative stress and increases survival after endotoxin.

Recombinant human mitochondrial transcription factor A protein (rhTFAM) was evaluated for its acute effects on cultured cells and chronic effects in mice. Fibroblasts incubated with rhTFAM acutely increased respiration in a chloramphenicol-sensitive manner. SH-SY5Y cells showed rhTFAM concentration-dependent reduction of methylpyridinium (MPP(+))-induced oxidative stress and increases in lowered ATP levels and viability.

The Alzheimer's disease mitochondrial cascade hypothesis.

We first proposed the mitochondrial cascade hypothesis of sporadic Alzheimer's disease (AD) in 2004. Our core assumptions were a person's genes determine baseline mitochondrial function and durability, this durability determines how mitochondria change with advancing age, and critical changes in mitochondrial function initiate other pathologies characteristic of AD. Since then several lines of investigation report data consistent with or supportive of our hypothesis.

The Alzheimer's disease mitochondrial cascade hypothesis: an update.

In 2004 we proposed the mitochondrial cascade hypothesis of sporadic Alzheimer's disease (AD). Our hypothesis assumed sporadic and autosomal dominant AD are not etiologically homogeneous, considered evidence that AD pathology is not brain-limited, and incorporated aging theory. The mitochondrial cascade hypothesis asserted: (1) inheritance determines mitochondrial baseline function and durability; (2) mitochondrial durability influences how mitochondria change with age; and (3) when mitochondrial change reaches a threshold, AD histopathology and symptoms ensue.

Mitochondrial gene therapy augments mitochondrial physiology in a Parkinson's disease cell model.

Neurodegeneration in Parkinson's disease (PD) affects mainly dopaminergic neurons in the substantia nigra, where age-related, increasing percentages of cells lose detectable respiratory activity associated with depletion of intact mitochondrial DNA (mtDNA). Replenishment of mtDNA might improve neuronal bioenergetic function and prevent further cell death. We developed a technology ("ProtoFection") that uses recombinant human mitochondrial transcription factor A (TFAM) engineered with an N-terminal protein transduction domain (PTD) followed by the SOD2 mitochondrial localization signal (MLS) to deliver mtDNA cargo to the mitochondria of living cells.

DNA extraction procedures meaningfully influence qPCR-based mtDNA copy number determination.

Quantitative real time PCR (qPCR) is commonly used to determine cell mitochondrial DNA (mtDNA) copy number. This technique involves obtaining the ratio of an unknown variable (number of copies of an mtDNA gene) to a known parameter (number of copies of a nuclear DNA gene) within a genomic DNA sample. We considered the possibility that mtDNA:nuclear DNA (nDNA) ratio determinations could vary depending on the method of genomic DNA extraction used, and that these differences could substantively impact mtDNA copy number determination via qPCR.

Oxidative stress, mitochondrial dysfunction, and stress signaling in Alzheimer's disease.

Although oxidative stress and mitochondrial dysfunction have been linked to neurodegenerative diseases such as Alzheimer's disease (AD), it remains unclear how mitochondrial oxidative stress may induce neuronal death. In a variety of tissues, cumulative oxidative stress, disrupted mitochondrial respiration, and mitochondrial damage are associated with, and may indeed promote cell death and degeneration. In this review, we examine current evidence supporting the involvement of mitochondria and mitochondrially generated stress signaling in AD and discuss potential implications for the mechanism of pathogenesis of this disease.

Cell and animal models of mtDNA biology: progress and prospects.

The past two decades have witnessed an evolving understanding of the mitochondrial genome's (mtDNA) role in basic biology and disease. From the recognition that mutations in mtDNA can be responsible for human disease to recent efforts showing that mtDNA mutations accumulate over time and may be responsible for some phenotypes of aging, the field of mitochondrial genetics has greatly benefited from the creation of cell and animal models of mtDNA mutation. In this review, we critically discuss the past two decades of efforts and insights gained from cell and animal models of mtDNA mutation.

Mitochondrial microheteroplasmy and a theory of aging and age-related disease.

We implicate a recently described form of mitochondrial mutation, mitochondrial microheteroplasmy, as a candidate for the principal component of aging. Microheteroplasmy is the presence of hundreds of independent mutations in one organism, with each mutation usually found in 1-2% of all mitochondrial genomes. Despite the low abundance of single mutations, the vast majority of mitochondrial genomes in all adults are mutated.

Development of mitochondrial gene replacement therapy.

Many "classic" mitochondrial diseases have been described that arise from single homoplasmic mutations in mitochondrial DNA (mtDNA). These diseases typically affect nonmitotic tissues (brain, retina, muscle), present with variable phenotypes, can appear sporadically, and are untreatable. Evolving evidence implicates mtDNA abnormalities in diseases such as Alzheimer's, Parkinson's, and type II diabetes, but specific causal mutations for these conditions remain to be defined.

A "mitochondrial cascade hypothesis" for sporadic Alzheimer's disease.

Alzheimer's disease (AD) includes etiologically heterogeneous disorders characterized by senile or presenile dementia, extracellular amyloid protein aggregations containing an insoluble amyloid precursor protein derivative, and intracytoplasmic tau protein aggregations. Recent studies also show excess neuronal aneuploidy, programmed cell death (PCD), and mitochondrial dysfunction. The leading AD molecular paradigm, the "amyloid cascade hypothesis", is based on studies of rare autosomal dominant variants and does not specify what initiates the common late-onset, sporadic form.

Inhibition by R(+) or S(-) pramipexole of caspase activation and cell death induced by methylpyridinium ion or beta amyloid peptide in SH-SY5Y neuroblastoma.

Cell models of neurodegenerative diseases (NDD) can involve expression of mutant nuclear genes associated with Mendelian forms of the diseases or effects of toxins believed to replicate essential disease features. Death produced by exposing neural cells to methylpyridinium ion (MPP(+)) or neurotoxic beta amyloid (BA) peptides is frequently used to study features of the sporadic, most prevalent forms of Parkinson's disease (PD) and Alzheimer's disease (AD), respectively. We examined in replicating SH-SY5Y human neuroblastoma cells the release of cytochrome C into cytoplasm, activation of caspases 9 and 3, and loss of calcein retention as markers of the "mitochondrial" pathway of cell death.